1. Field of the Invention
This invention relates to an improvement in a technique for manufacturing a vehicular body panel or component part.
2. Description of the Related Art
Japanese Patent Laid-Open Publication NO. HEI-10-129527, for example, discloses a hood made of plastic resin material for use in an automobile. The hood has a closed cross sectional structure which is made of a product formed by a blow technique and which has an outer skin and a stiffener integral therewith. The outer skin has a main body section having a central portion extending in a widthwise direction of a vehicle body, two side edge portions located at both sides of the central position and extending in a longitudinal direction of the vehicle body, and two connecting portions interconnecting the central portion and the respective side edge portions. Each connecting portion includes a reinforcement rib extending from the stiffener and deposited onto the outer skin. The reinforcement rib imparts increased rigidity to the hood.
The presence of the hood made of the panel formed by plastic resin material provides no difficulty in implementing the aforementioned deposition during the forming operation of the plastic resin or in heat fusion of the two members (i.e., the reinforcement rib and the outer skin). However, the hood made of a steel panel obtained by bending formation of the blank material is remarkably in wide use rather than the plastic panel. The hood made of the steel sheet encounters another issue different from the plastic panel. In particular, although it has been a usual practice to employ a structure wherein a reinforcement plate, which is called a backing plate, is attached to the steel panel with a view to mounting a hinge or striker to the hood panel, the presence of the backing plate formed of a curved plate encounters a problem during mounting the backing plate to the hood. This problem is more clearly described with reference to FIGS. 19A and 19B hereof.
As shown in FIG. 19A, a hood frame 201, formed by bending the steel blank material, and a steel backing plate 202, formed by bending the steel sheet to conform to the curved profile of the hood frame 201, are prepared and are brought into contact with one another as shown by arrow {circle around (1)}.
As shown in FIG. 19B, an edge of the backing plate 202 is connected to the hood frame 201 by a weld bead 203. Such a technique for connecting the backing plate is widely used in known practice. In such a mounting technique, it is required to separately form the hood frame 201 and the backing plate 202 separately by bending with a bending press or with a bending machine, respectively, requiring two separate bending steps.
In many cases the backing plate 202 has a larger thickness than that of the hood frame 201. There are some cases in which the backing plate 202 has a smaller thickness than that of the hood frame 201. In general, the thickness of the hood frame 201 is not necessarily equal to that of the backing plate 202. Since the steel plates suffer from spring back phenomenon (i.e., a slight amount of restoring of the press material after press forming step) different in magnitude from one another depending on the thickness and the bending radius, there exists a slight difference in the curved shape between the hood frame 201 and the backing plate 202. When reconciling or joining these components with such a difference in the curved shape, there exists an increased tendency wherein a gap is produced at corners 204,205. Although the backing plate 202 functions to locally reinforce the thin hood frame 201, the presence of the gap results in a decrease in the reinforcement effect.
In such a conventional manufacturing method described with reference to FIGS. 19A and 19B, the bending operation should be implemented in two steps, with a resultant increase in the fabrication cost and a resultant decrease in the reinforcement effect owing to the gap created between the hood frame and the backing plate.
Next, when an outer side panel of raw material is blanked out from a single stripped-shaped steel plate, a tail gate of the raw material is also concurrently blanked out with a view to improving the production yield with the use of a blanking method for a vehicle body, which is disclosed, for example, in Japanese Patent Laid-Open Publication No. SHO-58-128231. In this method, when the outer side panel of the raw material is sequentially blanked out from the steel plate, it is a usual practice to blank out left and right symmetrical divided raw material for lower halves of the tail gate raw material from the steel plate at a portion thereof corresponding to a blanking area to form a door mount section while blanking out left and right asymmetrical divided raw material for upper halves of the tail gate raw material from the steel plate between the outer side panels of the raw material remaining side by side. The two upper divided halves and the two lower divided halves are welded to one another to obtain the tail gate of the raw material. Thus, it is well known to cut out a piece from a scrap portion, which is produced during the blanking step of the vehicular body of the raw material, for utilizing the piece to manufacture component parts of the vehicle body for thereby improving the yield of the raw material.
In the above method, the outer side panel of the raw material, which is discharged from the blanking press, is then sequentially transferred through a drawing press, a trimming press and a piercing press to implement the contracting step, the edge cutting step and the aperture forming step, respectively, to complete the formation of the outer side panel. On the other hand, the two divided lower halves of the raw material and the two divided upper halves, both of which are discharged from the blanking press, are transferred to a welding site in another route, wherein these components are welded together to form the tail gate of the raw material.
Paying attention to the two divided lower halves and the two divided upper halves, it is required for a specific transfer means, which transfers these components, to be located so as to extend from the blanking press, with a resultant factor which reduces a work space around the blanking press.
Further, it is necessary for these components to be adequately managed to prevent the components from getting mixed with other components or from being lost.
In addition, it is necessary to prepare a temporary stock space in the welding site for the two divided lower halves of the raw material and the two divided upper halves, and another temporary stock space in the welding site for the completed tail gates of the raw material, occupying a relatively larger space for the welding site.
When trying to improve the yield of the raw material by cutting out a useful piece from the scrap portion in the aforementioned manner, it becomes necessary for a specific transfer means for the piece, a loss protective measure for the piece and the welding site in a large space to be provided, with a resultant increased cost in the equipment as well as an increase in an area for which the equipment is installed.